If you set the season to winter when using any season mod, rain is rendered instead of snow but snow layers still are placed, not a game breaking bug, but takes away from the immersion.

Can confirm this still occurs with particle rain + serene seasons on 1.21.

Within the serene seasons config, there's a boolean that can be used to determine whether it should snow in the biome or not depending on the season. That may be useful for adding serene seasons compatibility?
https://github.com/Glitchfiend/SereneSeasons/blob/77f6fb0aa0f284d0f5db75a9ec6c648ce879ed43/common/src/main/java/sereneseasons/config/SeasonsConfig.java#L104

Thanks for taking a look! I actually only need to make a trivial change because Serene Seasons handles this very sensibly but I won't promise support for other season mods.